DECLARE @xmlAttributeRelation XML

SET @xmlAttributeRelation='<attributeRelationRequest>
<Entity>1</Entity>
<Entity>2</Entity>
</attributeRelationRequest>'
	

	;WITH cte as
	( 
		SELECT 
			a.b.query('.') as Entity
		FROM @xmlAttributeRelation.nodes('/attributeRelationRequest') as a(b)
    )
	SELECT  c.d.query('.').value('.', 'INT') ItemID
    FROM
         cte
         CROSS APPLY Entity.nodes('/attributeRelationRequest/Entity') as c(d)

DECLARE @xmlAttributeRelation XML
SET @xmlAttributeRelation='<Entity>
<Entity>1</Entity>
<Entity>2</Entity>
</Entity>
'
SELECT Result = ent.val.value('.', 'int')
FROM @xmlAttributeRelation.nodes('/Entity/Entity') ent(val)

Result
-----------
1
2

(2 row(s) affected)